Bleaching bath and process for



Reissued Feb. 24, 1948 BLEACHING BATH AND PROCESS FOR BLEACHING COLOR FILM Frank J. Kaszuba, Binghamton, N. Y., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Original No. 2,419,900, dated Ap'ril' 29, 1947, Serial No. 627,527, November 8,1945. Application for reissue July 11, 1947, Serial No.

17 Claims.

This invention relates to photographic bleaching baths, to such baths employed in multicolor photography, and especially to baths for the bleaching of the silver image ina multicolorv film following color-forming development.

It is known" that in the processing of multicolorreversal film and multicolor negative film, the silver present in all the layers following development is converted intoasalt by any of the well-known silver salt formers, commonly known as bleaching baths, and the silver-salt thus formed'is then. removed by dissolving it in a silversalt solvent suchas, forv example, hypo, In oer-- taincolor photographic emulsions containing organic solvent for color-couplers, such as a Water-insoluble but Water permeable celluloze binder or a high-boiling crystalloidal material as described in United States-Patents 2,304,940 and 2,322,027, respectively, there is a tendency for these solvents to occlude the metallic silver following development and'to prevent its conversion into a silver salt by the customary bleaching bath. In the processes described in these patents, the coupler originally present in the emulsion layer and the dye formed fromit are dissolved in globules of" the organic solvent which traps or wets' the particles of metallicsilver as it is formed.

during the development step and then encloses portions of it which can no longer be al fectcd by the bleaching bath. Inorder to obviate this difficulty, it has been proposed in United States Patent 2,378,265 to incorporate into a bleach bath an organic solvent'such as a mcnohydrcxy alco- 1101 or an aliphatic ketone. These solvents permit the bleach bath to-penetrate any organic material in the emulsion so that the bleach bath is able to act on the metallic silver formed therein during development.

It has been found that in removing metallic silver from multicolor photographic layers, which are prepared by the direct dispersion of colorformers fast to diffusion in silver-halide emulsions' as disclosed. in United States Patents 2,179,228; 2,179,238-9; 2,179,234; 2,178,612; 2,179,244; 2,186,719; 2,186,851-2; 2,186,732-3-4; 2,186,849; 2,186,045; 2,200,306; 2,280,722; 2,292,575; 2,303,928; and 2,307,399,-bleaching poor color rendition. Moreover, the unremoved 2 in which it is located with the result that even the poor color rendition is finally obliterated.

An object of the present invention is .to pro vide solutions for the removal of metallic silver from multicolored photographic layers.

A further object is to provide a method and means for the complete removal of metallic silver from silver-halide emulsion layers containing dispersed color-formers fast to. diffusion.

Other objects and features of the invention will become apparent as the description proceeds.

I have found that the above objects are accomplished by incorporating into a bleach solution commonly known and used in color photography, 9. phenoxy alcohol represented by the following general formulae:

wherein R is an alkyl group, such as methyl, ethyl, propyl, and the like, X represents either hydrogen, an alkyl of the same value as R. or a halogen, such as bromine or chlorine, and n represents a positive integer of from 1130 3'.

This discovery makesit possible to enable the bleach bath to oxidize all of the metallic silver in the developed color film, and to permits its silver has a deteriorating action upon the layers complete removal from the photographic layers. Furthermore, it has been found that such alcohols may be utilized in the bleaching of silver from any color filmwhether the dyestutf images be formed while employing the color-former in the layer or while forming thedyestuff images by the methods known as the controlled difiusion method or the selected second exposure and color development method, as disclosed in United States Patents 1,897,866; 1,900,870; 1,928,709 and 1,980,941. In the latter cases, better results are often achieved when using bleaching baths containing these alcohols than when using the monohydroxy alcohols andv aliphatic ketones referred to in United States Patent 2,378,265.

The invention is accordingly generic to the re moval of silver from any photographic color film Where the dyestuff images are produced by colorforming development.

The concentration of the phenoxy alcohol required may vary considerably. For instance, as little as grams per liter of bleach solution has been found to efi'ect the complete conversion of metallic silver into a silver-salt soluble in the usual silver-salt solvent, and as much as 20 grams per litercan be used without interference with the properties of the bleaching solution. Amounts higher than 20 grams per liter can be employed, but the concentration actually employed should not exceed the solubility limits of the alcohol selected. For practical purposes, however, concentrations ranging from between 5 and 15 grams per liter are most desirable. These alcohols are readily removed in the subsequent washing of the film and do not leave oily slicks on the surface, nor do they effect the film base in any way.

The following are examples of phenoxy alcohols employed in accordance with the present invention:

B-(p-chlorophenoxy) ethanol O-CH:.CH.CH:

C H: 1 (p-methylphenoxy)-propanol-2 O-GHiLCHaOH I B-(P-metbyl phenoxy) ethanol O-GHI-CH-OHI l-phenoxy propanol-2 OCH|.CH.CH:

1 -(p-bromophenoxy)-propanol-2 OCH1.CH:CH1OH fl-phenoxypropanol The compounds and homologues thereof are prepared according to the method of A. J. Shukis et al., J. A. C. S., 66, page 1461, 1944.

As is well known, all bleach solutions contain an oxidizing agent dissolved in a suitable solvent, such as, for example, water, with or without the presence of other adjuvants. A typical bleach solution consists of 100 grams of an oxidizing agent per liter of solution, and may contain one or more of the following ingredients: Potassium bromide (converting agent) grams 10 Disodium phosphate (buffering salt).. do 40 Sodium bisulfate (buffering salt) do 5 Sodium tetraphosphate (corrosion preventive) grams 20 Water to make up (solvent) liter 1 By an oxidizing agent I mean an inorganic chemical compound that will oxidize a metallic silver image to form a silver-salt. Most commonly used oxidizing agents are alkali metal ferricyanides, such as sodium, potassium, ammonium ferricyanides, the alkali metal persulfates, i. e., the sodium and potassium persulfates, or mixtures of these salts.

By a converting agent I mean a chemical compound such as potassium bromide or sodium thiccyanate which by reason of a difference in solubility will replace the silver ferrocyanide formed in the bleaching reaction (when ferricyanide is used as the oxidizing agent) to form silver bromide or silver thiocyanate and thus impel the bleaching reaction to go to completion. Converting agents are sometimes called halogenizing agents.

By buffering agents I mean any substance that is added to bring the bleach solution to aspecified pH and to maintain this pH even though small amounts of acids or alkali may be carried into the bleach by the film. The pHs used in bleaching color films are generally maintained between 3 and 9.

By corrosion preventive I refer to those compounds which retard the corrosive effect of the bleach solution on developing tanks, trays, etc. Large quantities (20-80 grams per liter) of alkali metal phosphates such as disodium phosphate, sodium tetraphosphate, and the like, have been found to do this effectively as well as dialkyl amino alcohols as described in United States Patent 2,327,813.

By solvent I refer to the liquid in which the above materials are dissolved which is usually water.

The following examples describe in detail methods for accomplishing the above objects, but it is to be understood that they are inserted merely for purposes of illustration and are not to be construed as limiting the scope of the invention.

Example I Ob lhUIOoh-ON aque 01.15

Sodium sulfite ..grams .5 p-Amino diethyl aniline HCl do 4 Sodium carbonate do 40 Potassium'bromide do 1 Water to make up liter 1 water.

aqueous solu- Rinsed for 1 minute in running Hardened for 5 minutes in a 3% tlon of chrome alum.

Washed for 5 minutes in running water.

The first washed film was treated in solution No. 1 and the second Washed film was treated in solution No. 2 of the following compositions:

No. 1 No. 2

Dlsodlum monopotassium ferricyanide grams 100 100 Potassium bromide l do l 10 Sodium tetraphosphate do 20 20 Disodium phosphate .do 40 40 Sodium bisuliate d0 25 25 fl-phenoxyethanol... d o 10 Water to make up .liter 1 1 ihe two bleached film sheets were then washed in water for minutes, fixed for 5 minutes in a 20% aqueous hypo solution, washed for an additional 5 -minutes and then dried. The film bleached in solution No. 1 showed objectionable hazines due to the presence of metallic silver in the layers, whereas the film bleached in solution No. 2 containing c-phenoxyethanol was clear and of the desired color rendition.

Example II 'Two exposed 4" x 5" multilayer color film sheets of the negative type and containing colorformers fast to difiusion were processed as follows:

Developed for'lO minutes at 68 F. in a developer or the'followin'g composition: Sodium sulfite grams 0.5 2 amino-5-diethylaminotoluene hydrochloride grams 2.5 Hydroxylamine I-ICl do 1 Sodium carbonate do 65 Potassium bromide 1 do 2.5 Water to make up liter 1 of Short stopped for 5 minutes in a solution the following composition:

Monopotassium phosphate grams 80 Disodium phosphate .do 20 Water to make up liter 1 Hardened for 3 minutes in a 3% chrome alum solution.

Washed for 5 minutes in running water.

The first washed film was treated in solution No. 1 and the second washed film was treated in solution No. 2 of the following compositions:

No. 1 No. 2

Potassium ferrlcyanide "grams" 100 100 Disodium phosphate... ..do-" 4.3 4.3 Monopotassium phosphate do.. 5. 8 5.8 Potassium bromide do 10 10 l-(p-bromophcnoxy)-propanol 60.-.- 10 Water to make up litet 1 1 6 The two bleached sheet films were'then washed for '5 -minute's, fixed for '5 minutes in a 20% aqueous solution of hypo, washed an additional 15 minutes and then dried. As in Example -I, the film bleached in solution No. 1, containing no 1 (p-bromophenoxy) -propanol-2 showed considerable haziness, whereas the film bleached in solution No. 2 was clear and of the desired color rendition.

Example III Example I was repeated with the exception that the bleach bath No. 2 contained 10 gramsof c-phenoxypropanol instead of p-phenoxyethanol. The film bleached in the solution containing no p-phenoxypropanol showed objectionable hazi ness, while the film bleached with the solution containing e-phenoxy-propanol'was clear and of the desired color rendition.

The above specific examples are toloe regarded as merely illustrative of the invention, andnot in any Sense restrictive. It will be obvious to anyone skilled in the art that many modifications such as substituting equivalent materials and varying the proportions of materials used are within the spirit and scope of the invention as defined in the appended claims I claim:

1. In a process of color photograph the meth- 0d of removing silver from the film after dyestufi image formation by the action of a bleaching bath which comprises treating said film with such a bath containing a phenoxy alcohol selected from the class consisting of those corresponding to the following formulae:

(g-(CHD "OH the class consisting of hydrogen, alkyl, and halogen, and n is a positive integer of from 1 to 3.

2. In a process of color photography the method of removing silver from a color film containing dyestufi images which are produced by color-forming development of an emulsion containing 21. dyestufi former fast to diffusion, the improvement which comprises subjecting said film to the action of a bleaching bath containing a phenoxy alcohol selected from the class consisting of those corresponding to the following formulae:

( J- enema and o-cmoH-R wherein R is alkyl,- X is a member selected from the class consisting of hydrogen, alkyl, and halogen, and n is a positive integer of from 1 to 3. 3. In a process of color photography the methnoxyethanol.

4. 'In a process or fi-phenoxyeth'anol.

7. In a process of color photography the methof removing silver by the action of a bleaching bath which comprises adding to said bath 1- (p-methylphenoxy) -propanol-2.

8. In a, process of color photography the method of removing silver by the action of a bleaching bath which comprises adding to said bath wherein R is alkyl, X is. a member selected from 11. A photographic bleaching bath comprising an aqueous solution of an inorganic oxidizing agent and p-phenoxyethanol.

12. A photographic bleaching bath comprising an aqueous solution of an inorganic oxidizing agent and l-(p-methylphenoxy) -propanol-2.

13. A photographic bleaching bath comprising an aqueous solution of an inorganic oxidizing agent and fi-phenoxypropanol.

of a bleaching bath applied subsequent to the color development ste the improvement which comprises removing the silver by the action of a bleaching bath containing a phenoxy alcohol selected from the class consisting of those corresponding to the following formulae:

wherein R is alkyl, X is a member selected from the class consisting of hydrogen, alkyl, and halogen, and n is a positive integer of from 1 to 3.

15. In a process of producing photographic color images in a silver-halide emulsion by colorforming development in which silver images produced in the process are removed by the action of a bleaching bath applied subsequent to the color development step, the improvement which comprises removing silver by the action of a bleaching bath containing p-phenoxyethanol.

16. In a process of producing photographic color images in a silver-halide emulsion by colorforming development in which silver images produced in the process are removed by the action of a bleaching bath applied subsequent to the color development step, the improvement which comprises removing silver by the action of a bleaching bath containing l-(p-methyl-phenoxy) -propanol-2.

17. In a process of producing photographic color images in a silver-halide emulsion by colorforming development in which silver images produced in the process are removed by the action of a bleaching bath applied subsequent to the color development step, the improvement which comprises removing silver by the action of a bleaching bath containing fi-phenoxypropanol.

- FRANK J. KASZUBA. 

